Forging a five-decade career as an actor and director in both television and films, Wanamaker started in 1948's My Girl Tisa playing Mark Denek. He went on to appear in The Competition (1980), Irreconcilable Differences (1984), Superman IV: The Quest for Peace (1987), and Baby Boom (1987, series 1988). Between acting gigs, Wanamaker also directed a mix of films, TV shows and TV series including the popular Hart to Hart series (1979–83).